Newton’s Telescope in Print: The Role of Images in the Reception of Newton’s Instrument Sven Dupré Ghent University While Newton tried to make his telescope into a proof of the supremacy of his theory of colours over older theories, his instrument was welcomed as a way to shorten telescopes, not as a way to solve the problem of chromatic aberration. This paper argues that the image published together with the report on New- ton’s telescope in Philosophical Transactions (1672) encouraged this recep- tion. The differences between this visualization and other images of Newton’s telescope, especially that published in Opticks (1704), are discussed. This paper shows that the image in Opticks adopted characteristics of a Carte- sian program of visualization of machines and instruments which comple- mented a rhetoric which attributed primacy to theory over practice. The dif- ferences between the images in Philosophical Transactions and Opticks are also considered within the broader institutional context of Newton’s atti- tude towards the Royal Society. Introduction In a seminal article on the telescope in the seventeenth century Albert Van Helden complained that “the traditional treatment of the telescope is re- plete with optical diagrams...with the result that one is left with the impression that the telescope was an instrument which, if not invented through science, was at any rate turned into the sophisticated instrument it became by science—the science of optics” (Van Helden 1974, p. 38). Van Helden convincingly argued for the important contribution of craft skills—which could not be represented in optical diagrams—to the devel- opment of the telescope in the seventeenth century. Moreover, as I will ar- gue here, the modernized optical diagrams also hardly do justice to the vi- The author is a Postdoctoral Fellow of the Research Foundation—Flanders. This work has been supported by the award of a Research Grant of the Research Foundation—Flanders. Perspectives on Science 2008, vol. 16, no. 4 ©2008 by The Massachusetts Institute of Technology 328 Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/posc.2008.16.4.328 by guest on 29 September 2021 Perspectives on Science 329 sualizations which historical actors used to communicate on the telescope with patrons, mathematicians, and craftsmen. A lack of attention to the historical and visual particulars of the communication on this instrument deprives us of information on the conceptualization and reception of the telescope in the seventeenth century. In this paper I will focus on Newton’s telescope. I will consider three different drawings of Newton’s telescope: (1) the drawing based on the formal description by Henry Oldenburg, which was checked by Newton and published in a modiªed version in the Philosophical Transactions of 25 March 1672 (Newton 1672)1; (2) an unªnished draft of a description of the telescope in Newton’s papers at the Cambridge University Library; and (3) the drawing of Newton’s telescope published in the Opticks (1704).2 Earlier comments on these drawings explained the differences be- tween these drawings in terms of assumed inaccuracies in the engravings or in terms of differences in the instruments themselves (Mills and Turvey 1979, p. 136; Hall 1995, p. 76). Such comments are based on analyses of the drawings which—implic- itly or explicitly—aimed at a reconstruction of the state of the technology. Unlike such analyses my approach will try to understand the function of the visualizations of Newton’s telescope for the historical actors them- selves.3 I will ask questions about how the maker of the drawing, the mes- sage, and the audience of the drawing interacted in the communication of the drawing. It is my aim to understand the differences between the visu- alizations of Newton’s telescope in terms of the different functions of the drawings. What did the maker of the drawing try to communicate? How did the audience understand the message communicated by the drawing? My analysis will stress the role of images of Newton’s telescope in the re- ception of the instrument. In following this approach I am not looking for the development of some presumed ‘correct’ representation of the telescope. The way of rep- resenting a telescope was a problem whose solutions depended on the function of the representation. In the seventeenth century the telescope 1. Oldenburg sent a verbal description and a picture of Newton’s telescope—based on the telescope which Newton had presented to the Royal Society—to Newton for correc- tions on 2 January 1671/2. Newton replied with corrections, which Oldenburg included in the formal description published in Philosophical Transactions, on 6 January 1671/2. Oldenburg sent the description and picture to Huygens on 15 January 1671/2 (Turnbull 1959, pp. 72–76, pp. 79–82). 2. A fourth drawing of Newton’s telescope (by Newton) is now in the Bernouilli papers in Basel, but in the 18th century it was in the possession of Johann Jacob Huber who worked at the Royal Observatory in Greenwich (Cohen 1993). As the original function of this drawing is unclear, I will leave it out of the discussion here. 3. This approach is indebted to Popplow 2004. Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/posc.2008.16.4.328 by guest on 29 September 2021 330 Newton’s Telescope in Print presented problems of representation which were speciªc to this optical in- strument. The problems were different from those involved in depicting mathematical instruments, which had received attention in the sixteenth century. With mathematical instruments the boundary between the ‘illus- tration’ of the instrument in the book and the actual instrument was often blurry. The boundary case was, of course, paper instruments (Bennett 2003).4 However, with the telescope the visual description of the construction and manipulation of the instrument did not coincide with a description of the mathematical or optical knowledge embodied in the instrument. In brief, there were no such things as paper telescopes. This is not to say that the solutions given to the problems of represent- ing telescopes in the seventeenth century did not show any continuity with those already found in representing mathematical instruments in the sixteenth century. In Selenographia (1647) and—even more obviously—in Machina coelestis (1673) Johannes Hevelius presented pictures of the tele- scopes, shown in the context of his observatory Stellaeborg in Danzig, which were modelled on Tycho Brahe’s (Figure 1). Such pictures were sup- posed to vouch for the quality of the instruments (Winkler and Van Helden 1993; Van Helden 1994). This type of visualization—which, ac- cording to Martin Kemp (1996), allows mathematics to partake in the rhetoric of the real—had become the most authoritative one in a process that extended over the past two centuries. In Dupré 2006 I have argued that there were more options available in the representation of optical instru- ments in the ªfteenth and sixteenth century than this one. There were also more possibilities in the representation of telescopes than the one aimed at virtual witnessing chosen by Hevelius.5 First, I will discuss the visualization of lens-grinding machines in the seventeenth- century. The depiction of machines is hardly new to the seventeenth cen- tury, but the legacy of Descartes’ program for the mechanisation of lens- grinding had speciªc visual characteristics which complemented a rheto- ric which attributed primacy to theory over practice.6 I will show that this type of visualization and rhetoric was adopted by Newton in the represen- tation of his telescope in Opticks. In the second part of my paper I will look at the differences with the representation in Philosophical Transactions. 4. On paper instruments, see Gingerich 1993. 5. The term virtual witnessing is used in this context in Winkler and Van Helden 1993, pp. 99, 111. 6. The scholarship on early modern machine drawings is extensive. A good, recent starting point is the various contributions to Lefèvre 2004. Leonardo’s drawings of ma- chines for making mirrors from the late ªfteenth and early sixteenth centuries are the ex- ception to the general observation that no drawings of mirror or lens-grinding machines pre-dating the invention of the telescope are preserved (Dupré 2005). Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/posc.2008.16.4.328 by guest on 29 September 2021 Perspectives on Science 331 1. A Cartesian Program of Visualization and Newton’s Telescope in ‘Opticks’ Recently, Graham Burnett (2005) has discussed Descartes’ program of the mechanisation of lens-grinding and its legacy in the seventeenth century in detail. I will rely here on Burnett’s account, but I will focus, in particu- lar, on the issues of visualization which were involved in the communica- tion of the machines devised to grind (hyperbolic) lenses. Burnett has convincingly shown that Descartes’ program relied on a distrust of the lens-grinding skills of artisans.7 I will show that this rhetoric and style of visualization return in Newton’s Opticks. In the 1620s Descartes found a solution to the problem of the anaclastic (Shea 1991, pp. 149–163). He showed that the shape of the curved surface necessary to refract a set of parallel rays to a single point was hyperbolic. With this solution to the problem of the anaclastic Descartes stood at the beginning of a tradition which considered the grinding of hyperbolic lenses the main route to the perfection of the telescope until Newton’s dis- covery of the compound nature of light. The grinding of hyperbolic lenses was difªcult and Descartes’ mathematics did not play any role in the im- provement of the telescope in the seventeenth-century.